1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor laser device. More particularly, the present invention relates to a semiconductor laser device and method of manufacturing the same that can prevent alignment error when defining the location of a P-type metal.
2. Description of the Related Art
In the conventional method of fabricating a 2˜5 μm ridge type waveguide laser, it is difficult to position the P-type metal accurately on top of an protrudent platform of the ridge type waveguide laser because the area at the top surface of the protrudent platform is extremely small.
FIG. 1 is a schematic cross-sectional view showing a conventional semiconductor laser device in the process of defining the location of a P-type metal. As shown in FIG. 1, an epitaxial layer 100 is shaped into a ridge structure 106 comprising two channels 102 and an protrudent block 104. Thereafter, a P-type metal 108 is defined on the protrudent block 104. However, an accurate alignment of the P-type metal 108 is difficult because the top area of the protrudent block 104 is very small.
FIG. 2 is a schematic cross-sectional view showing another conventional semiconductor laser device in the process of defining the location of a P-type metal. As shown in FIG. 2, an epitaxial layer 200 is shaped into a ridge structure 206 comprising two channels 202 and a protrudent block 204. Thereafter, an insulating layer 210 is formed over the epitaxial structure 200 and then photolithographic and etching processes are carried out to expose the area for forming the P-type metal. However, due to possible misalignment in the process of defining the insulating layer 210, the top surface of the protrudent block 204 may not be accurately exposed. Consequently, a subsequently formed P-type metal will not fully contact with the top surface of the protrudent block 204.
At present, one of the solutions is to reduce the size of the P-type metal. FIG. 3 is a schematic cross-sectional view showing yet another conventional semiconductor laser device in the process of defining the location of a P-type metal. As shown in FIG. 3, an epitaxial layer 300 is shaped into a ridge structure 306 comprising two channels 302 and a protrudent block 304. Thereafter, an insulating layer 308 is formed over the epitaxial structure 300. Photolithographic and etching processes are carried out in sequence to expose the area for forming the P-type metal. After that, a P-type metal 310 is formed on the exposed surface of the protrudent block 304. Although this method is capable of reducing alignment errors, the P-type metal covers only a portion of the top surface of the protrudent block 304 within the ridge structure 306. In other words, the P-type metal will have a higher ohmic contact resistance and a lower heat-dissipating capacity.